Preparation of sulfur containing dicarboxylic acids



Patented Sept. 28, 1948 PREPARATION OF SULFUR CONTAINING DICARBOXYLIC ACIDS Thomas L. Gresham and Forrest W.

Shaver,

Akron, Ohio, assignors to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing.

2 Claims. 1

This invention relates to the preparation of certain sulfur containing dicarboxylic acids and is particularly concerned with the preparation of such compounds by the reaction of mercapto carboxylic acids with beta-propiolactone.

In our copending application Ser. No. 620,660, filed October 5, 1945, we have disclosed that betapropiolactone reacts at the mercapto group with mercaptans in which all hydrogen atoms except those attached to carbon are present in mercapto groups, to formbeta-thio carboxylic acids. It is also disclosed in the copending application of Thomas L. Gresham and Jacob Eden Jansen, Ser. No; 620,658, filed October 5, 1945, that beta-propiolactone reacts with salts of carboxylic acids at the carboxylic acid group to produce betaacyloxy carboxylic acid compounds.

By this invention we have discovered that when beta-propiolactone is reacted with a compound containing both a mercapto group and a carboxylic acid group, that is, a compound of the structure 4 wherein R is adivalent hydrocarbon radical, reaction occurs ilrst at the mercapto group; and that accordingly when substantially equimolecu lar proportions of the reactants are employed, the product consists exclusively of a sulfur containing dicarboxylic acid of the formula wherein R, as before and whenever appearing hereinafter, designates a divalent hydrocarbon radical.

The reaction between beta-propiolactone and a mercapto carboxylic acid requires no special conditions; it occurs whenever it is possible to bring the reactants into effective contact with one another. Thus, simply by mixing the reactants in any desired manner and heating the mixture in the absence of added materials, or by refluxing a solution of the reactants in an inert solvent such as benzene, ether, chloroform or the like, it is possible to obtain the desired dicarboxylic acid. Higher yields, however, are generally. secured by carrying out the reaction in a polar solvent for the reactants such as water, alcohols or the like and, preferably, in the presence of an equimolar proportion of an inorganic base such as an alkali metal hydroxide or ammonium hy- Application November 28,1945, Serial No. 631,499

2 droxide. When the reaction is effected in this way it is preferable first to prepare an aqueous solution containing the mercapto carboxylic acid and the base, to add the lactone to this solution and then to acidity the solution whereupon the sulfur-containing dicarboxylic acid is generally liberated as an insoluble material.

Other conditions for the reaction such as temperature and. pressure are not critical and may be varied widely. It is generally most convenient to operate at temperatures from 0 to 100 C. and at atmospheric pressure, but temperatures as low as C. or lower or as high as 200 C. or higher and pressures considerably above or below atmospheric are also operable. When the reaction is effected in solution in a polar solvent, temperatures from 0 to 50 C. are particularly eiTectlve' in producing highest yields of the dicarboxylic acid.

" ether.

To illustrate the invention in morespeciflc detail the following examples are cited, it being understood that the invention is by no means limited thereto. In the examples all parts are by weight.

Example 1 An aqueous solution is prepared by admixing 53 parts (0.5 mole) of thiohydracrylic acid with parts of an aqueous solution containing 20 parts (0.5 mole) of sodium hydroxide. To this solution there is then slowly added over a period .of about an hour 36 parts '(0.5 mole) of beta-pro- Example 2 53 parts of thiohydracrylic acid are dissolved in 35 parts of water and 36 parts of beta-propiolactone are then added thereto, the temperature of the solution during the addition being about 30-40 C. The reaction mixture. is allowed to stand at .room temperature for two days, whereupon a solid separates from the solution. The solid is filtered and recrystallized from a mixture of methanol and benzene. 12.2 parts of betaseparates which V 3 i thiodipropiohic acid (M. P. 120* C.) are thus obtained.

Example 3 by ethanol in this example similar results are obtained.

Example 4 A mixture of 53 parts of thiohydracrylic acid and 36 parts of beta-propiolactone is dissolved in 100 parts of chloroform and the solution refluxed for about 2 hours. A part of the chloroform is then distilled and the solution cooled whereupon beta-thio dipropionic acid crystallizes from the solution in about 36% yield.

When any of the above examples, illustrating variations in reaction conditions and procedures, is repeated under the same conditions using other mercapto carboxylic acids of the formula in place of thiohydracrylic acid, other sulfur containing dicarboxylic acids of the formula are secured in about the same yield. For example, when thioglycollic acid (mercapto-acetie acid) is used in place of thiohydracrylic acid, carboxymethyl beta-carboxy-ethyl sulfide is obtained. Other mercapto-carboxylic acids which may be substituted for thiohydracrylic acid include thiolactic acid, alpha-mercapto butyric acid, beta-mercapto-isobutyric acid, alpha-mercapto-lauric acid, thioricinoleic acid, thiosalicylic acid, o-mercapto-alpha-toluic acid, and the like. All these mercapto carboxylic acids possess the general formula where R is a divalent hydrocarbon radical (which may be either aliphatic or aromatic, saturated or unsaturated in nature) and all produce when reacted with beta-propiolactone sulfur containing dicarboxylic acids having a structure the same as the mercapto-acid except that the hydrogen atom of the mercapto group is replaced by the beta-carboxy-ethyl radical.

The sulfur containing dicarboxylic acids produced according to this invention are useful in the preparation of other organic compounds, for example, in the preparation of plasticizers, and are also useful in the rubber and plastics industries.

Numerous variations and modifications in the invention will be apparent to those skilled in the art and are within the spirit and scope of the appended claims.

We claim:

1. The method of preparing beta-thio dipropionic acid which comprises reacting thiohydracrylic acid and beta-propiolactone in aqueous solution in the presence of an alkali metal hydroxide, and then acidifying the solution.

2. The method of preparing a sulfur-containing aliphatic dicarboxylic acid of the formula wherein R is a divalent aliphatic hydrocarbon radical containing from 1 to 17 carbon atoms which comprises reacting a mercapto-substituted aliphatic earboxylic acid of the formula ns a-rr-on REFERENCES CITED The following references are of record in the file of this patent:

Chemische Zentralblatt 87 (1916), pp. 557, 558. 

